As known, the nozzle is designed to be axially mobile, in its entirety or partially, above the blowing mold between an upper position or raised position in which the nozzle is not functional (opening and closing of the mold allowing the loading of a blank and the release of the molded container) and a lower position or blowing position in which the end of the nozzle cooperates sealingly either with the neck of the blank, or with the face of the mold above which the neck of the blank projects and in which the nozzle is functional.
Blowing devices are known in which the end of the nozzle, in the functional position, cooperates positively with the neck of the blank and either sealingly abuts against the lip (edge) of the neck of the blank, or is sealingly fitted into or onto the neck of the blank.
Blowing devices are also known in which the end of the nozzle is configured in the shape of a bell which is larger than the neck of the blank and caps said neck by being sealingly supported at the front against the face of the mold on which the neck of the blank projects (see, for example, the document FR 2 764 544).
A blowing sequence normally consists of a step of pre-blowing the blank by means of a fluid (generally air) at moderate pressure (for example 7×105 Pa), then the blowing step itself, at high pressure (for example 40×105 Pa) generally accompanied by mechanical axial stretching by means of a stretch rod and finally an exhaust step with the discharge of the pre-blowing/blowing air. For these various steps, three respective solenoid valves are controlled sequentially which, on the one hand, are respectively connected to a source of fluid at moderate pressure, a source of fluid at high pressure and an exhaust and which, on the other hand, are connected to the nozzle.
A blowing device of the type under consideration consumes a very large amount of pressurized fluid, whether at moderate or high pressure. The constant production of pressurized fluid (air) in large quantities leads to a very high consumption of electrical energy for the functioning of the compressor(s). As a result, there is a constant and urgent demand on the part of the users of these blowing devices for as large a reduction as possible of the quantity of pressurized fluid used, so as to reduce the consumption of electrical energy.
It must be understood that the only useful volume for the blowing operation is the volume of the container forced into its final shape against the walls of the molding cavity of the mold, in other words, substantially the volume of the molding cavity. In contrast, all the volumes located between the outlet of the pre-blowing or blowing solenoid valve and the neck of the container are, strictly speaking, volumes which are superfluous for the deformation of the blank and are therefore dead volumes. At each step for pre-blowing and blowing a blank, these dead volumes are filled with pressurized fluid in the same manner as the useful volume, which involves a production of pressurized fluid which is substantially greater than the actual requirement. The dead volumes are of a size which is not inconsiderable relative to the useful volumes and any reduction of these dead volumes proves beneficial in terms of a possible reduction in the power of the fluid compressor and therefore of its cost, and in terms of reducing the electrical energy required for the functioning of the compressor.
In a first design of the blowing device, the solenoid valves were grouped together on a fixed base mounted on the frame remote from the nozzle. A flexible tube connected the common outlet of the solenoid valves to the connecting aperture of the nozzle (for example the tube 23 in FIG. 1 of the aforementioned document FR 2 764 544). In this design, the dead volume was very large, in particular due to the presence of the flexible tube for remote connection.
In a subsequent design, the dead volume has been markedly reduced by eliminating the flexible connecting tube and by mounting the solenoid valve block directly on the body of the nozzle, at the location for connecting the tube 23 in FIG. 1 of the document FR 2 764 544. Nevertheless, in this design which currently continues to exist, the juxtaposition of the two respective bodies of the solenoid valve block and of the nozzle further necessitates fluid passages of a sizeable length, which results in a dead volume which is still too large in terms of consumption. As a result, users uphold their demand for a still lower consumption of pressurized fluid, so as to reduce further the consumption of electrical energy.
Furthermore, the presence of solenoid valve blocks located remotely from the nozzle or juxtaposed therewith leads to a heavy and awkward assembly.